1. Field of the Invention
The invention relates to a conveyor mat for conveying products in a conveying direction between at least two divert wheels, comprising a number of plastic modules succeeding each other in conveying direction and extending transversely to the conveying direction, which modules, viewed in conveying direction, each have their front and rear sides provided with hinge loops, the hinge loops of modules that succeed each other in conveying direction cooperating and being coupled by means of hinge pins extending transversely to the conveying direction, which modules are each provided with through openings extending substantially transversely to the conveying face and of which modules the top faces together constitute a conveying face.
The invention also relates to a conveying system, comprising an endless conveyor mat extending between at least two divert wheels, for conveying products between the divert wheels in a conveying direction, which conveyor mat comprises a number of plastic modules succeeding each other in conveying direction and extending transversely to the conveying direction, which modules, viewed in conveying direction, each comprise hinge loops at their front and rear sides, the hinge loops of modules that succeed each other in conveying direction cooperating and being coupled by means of hinge pins extending transversely to the conveying direction, of which modules the top faces together constitute a conveying face and which modules are each provided with through openings extending substantially transversely to the conveying face, and which conveying system further comprises a slide-over device for transferring, adjacent a divert wheel from or towards the conveying face, products conveyed by the conveyor mat towards or from said divert wheel.
2. Description of Related Art
Such conveyor mats and conveying systems are known and are used for conveying all kinds of products in a large number of different environments. A particularly exacting application of such conveyor mat and such conveying system concerns the transport of products through a pasteurizer for pasteurizing the products.
During pasteurization, products, in particular beverages, after having been introduced into a package, are heated for some time so as to prolong the storage life of the products. To that end, the sealed packages containing the product are placed on a conveying track and passed through an encasing forming a long, watertight tunnel. The conveying track often has a length of 25-35 m and a width of 3-5 m. The conveying track passes the products within the tunnel along a number of zones where warm water having per zone a different temperature is sprayed onto the packages, for instance 20-40-60-80-60-40.degree. C. Such conveying track conveys the products at a speed of about 0.5-1 m/sec and has a capacity of about 30-70,000 packages per hour. In the temperature zones, about 25 m.sup.3 water per hour is sprayed onto the products per m.sup.2 track surface area. In order to use the water more efficiently, the conveying track is preferably of a double-decked design. The packages conveyed through the pasteurizer by means of the conveying track are usually pots or bottles manufactured from metal, plastic or glass.
In the known conveyors, as conveying track, endless conveyor mats are often used which are built up from a fabric of stainless steel wires. A drawback thereof is that such conveyor mats are expensive to purchase. Moreover, these conveyor mats are not of modular construction, as a consequence of which the repair of a damage in such conveyor mat is a time-consuming operation that has to be performed by a specialist.
Another type of conveying track used for conveying products through a pasteurizer is a walking beam, where the conveying track is formed by a number of juxtaposed even and uneven rows of beams succeeding each other in conveying direction, with the juxtaposed rows of beams overlapping each other in length. By means of crank-connecting rod mechanisms, the beams are reciprocated in such a manner that the products are in each case lifted by the even rows of beams and deposited on the row of uneven beams that follows in conveying direction, and so forth. Not only is such apparatus very expensive to purchase and maintain, also the chance of damage to the package and/or the product is substantial, because of the product each time being lifted and deposited within the pasteurizer.
For reasons of cost, attempts have been made to design the conveying track as an endless conveyor mat circulating in a conveying direction between a first divert wheel and a second divert wheel. Such a conveyor mat is known from U.S. Pat. No. 4,051,949. The conveyor mat is built up from a large number of interconnected plastic modules, each built up from a number of fins extending in parallel, side by side relationship in conveying direction. A number of these fins are provided with a raised rib. The top sides of these raised ribs together constitute a substantially ribbed conveying face built up from laterally staggered ribs which partially overlap in conveying direction. Adjacent the divert wheels, the products are transferred towards or from the conveying face by a slide-over device comprising a comb having a flat part carrying tooth-shaped projections. The teeth project between the raised ribs so that during discharging, the foremost products are transferred from the conveying face and pushed onto the flat part of the comb via the teeth by the following products, while via the second divert wheel, the modules continue their endless path. During the supply of products, the foremost products are pushed, at the location of the first divert wheel, from the flat part of the comb onto the conveying face via the teeth by following products.
A drawback of the known lamellar, plastic conveyor mat is that because of the high temperatures to which the conveyor mat is exposed in the pasteurizer, and because of the substantial pulling force exerted on the conveyor mat, this mat is insufficiently stretch and wear resistant.
Another drawback of the known plastic conveyor mat and of the known conveying system is that they are not suitable for conveying glass packages through a pasteurizer. As it is, during pasteurization, the pressure in the package increases. This may lead to breakage of about 1% of the glass packages as a consequence of weak spots in the glass and/or an unduly high filling degree of the package. In the known conveyor mat and in the known conveying system, the glass fragments of the broken packages get stuck in the ribbed conveying face, i.e. between the ribs and/or fins of successive modules, causing the modules to damage each other and/or the divert wheels. Moreover, large, flat fragments of glass fall through the spaces located between the fins of the modules and onto the inner side of the returning part of the conveyor mat, so that such fragments, when arriving at a divert wheel again, damage the modules and/or the divert wheel. The slide-over device gets damaged as well. In particular, the teeth of the comb break off or are bent by glass fragments stuck between the ribs and/or the fins, as a result of which they form an obstacle to the packages. Further, glass fragments may accumulate under the flat portion of the comb of the slide-over device, causing the comb to rise in the conveying plane and the teeth to form an obstacle to the products. Hence, in practice, in a pasteurizer for products packed in glass packages, plastic mats and/or such conveying systems are hardly used as conveying track. This is also the case when plastic conveyor mats and/or such conveying systems are used in other circumstances where high requirements are imposed on the temperature resistance, wear resistance and sturdiness.